The biosynthesis of porphyrins, corrins, heme and chlorophyll will be studied by 13C-FT NMR spectroscopy at the whole cell and cell-free levels. The structure of cobalt-free corrinoids will be determined. Large samples of 13C-labelled ALA and PBG will become available for studying porphyria. Mutants of P. shermanii which are deficient in B12 production are being examined to detect novel intermediates in the biosynthesis of the vitamin.